Stamping die for marking hot metal objects



United States Patent [56] References Cited UNITED STATES PATENTS 8/1877 Casilear.v...........r.....

Alfred Teplitz Pittsburgh, Pennsylvania. 730,868

[72] Inventor l01/28X 101/28X 792,781 6/1905 Lentz...................... 12/1912 Duncan....... 3/1917 Baskett................... 2/1918 Varga.... /1 33 Fowler.................... /1934 VanCant0rt.........r... 9/1936 Weindeletal............ 4/1943 Bastowetaluunl...

Primary Examiner- William B. Penn Auomey- Martin J. Carroll [21 Appl. No. [22] Filed May 21, 1968. [45] Patented Oct. 6, 1970 [73] Assignee United States Steel Corporation a corporation of Delaware G HOT METAL y suitable for markin primary character and a rou closely primary char er width than [54] STAMPING DIE FOR MARKIN OBJECTS 4 Claims, 4 Drawing Figs.

ABSTRACT: A stamping die particularl nded I0l/28 hot steel has a rou nded- B4411 5/02 surrounding the prima secondary character ry 101/28, 29, character with the acter having greater height 3, 4, 398, 399, 372 and preferably great the secondary character.

[51] Int. [50] Field Patented Oct. 6, 1970 llWE/VTDR ALFRED TEFL/T2 y 3 Z Attorney STAMPING DIE FOR MARKING HOT METAL OBJECTS This invention relates to a stamping die and more particularly to a die for marking hot steel. Stamping dies are used to apply identifying marks to many products. The character corresponding to the identifying mark is raised from a generally flat surface at one end of the die and the mark is applied by means of pressure or a blow at the other end of the die. The mark disrupts the continuity of the surface of the object being marked and thus produces a stress raiser". Under cyclic working loads, stress concentrations are produced at the mark which shorten the fatigue life of the marked object.

I have found that the deleterious effect of stamped markings on the fatique life of the marked object can be greatly reduced by closely surrounding the character on the die with a secondary character having less height than the primary character.

It is therefore an object of my invention to provide a stamping die which causes less damage to the object being marked than standard dies.

Another object is to provide such a die which better controls the penetration of the die in the workpiece.

These and other objects will be more apparent after referring to the following specification and attached drawing, in which:

FIG. 1 is a perspective view ofa die of my invention;

FIG. 2 is a sectional view taken on the line Il-Il of FIG. 1;

FIG. 3 is a view of a workpiece with a mark made therein with a die of my invention and with stress lines indicated thereon; and

FIG. 4 is an exploded perspective view of a plurality of dies mounted in a holder.

Referring more particularly to the drawing, reference numeral 2 indicates a die having a body 4 with a generally flat surface 6 at one end. A primary character 8 shown as the figure l extends outwardly from the surface 6 and is closely surrounded by a secondary character 10 which has less height and preferably less width than the primary character. It is also greatly preferred to have both the primary and secondary characters rounded as shown in FIG. 2 so that the combined characters are generally sinusoidal in cross section. The secondary character may closely approximate the shape of the primary character or may depart somewhat therefrom. Thus, as shown in FIG. 1, primary character 8 in the form of the FIG. I is surrounded by the secondary character 10 in the form ofa quadrilateral. The body and characters are preferably made of hardened steel. I

In operation, the die 2 is held with the character end against workpiece W and a blow struck against the other end. This produces a groove G of maximum depth and grooves G1 and G2 on opposite sides thereof. When the primary character penetrates the workpiece W to the extent that the secondary character contacts the workpiece, the suddenly increased contact area sharply increases the resistance to further penetration of the die. Thus, there is less likelihood of marking too deeply when excessive force is applied to the die 2. As shown in FIG. 3 by means of stress lines S, there is little stress concentration in the workpiece as compared to the stress concentration with standard dies. It is also contemplated that a plurality of dies be nested together in any suitable manner. For example, they may be nested as shown in FIG. 4. As there shown, six dies 10 to 15 are provided with characters 0, 4, 8, l, 3 and 7, respectively, thereon. As will be noted, the shapes of the secondary characters vary somewhat, but in all cases they closely surround the associated primary character and are of less height. The dies 10 to 15 are mounted in a holder including a body member 16 having a recess 18 for receiving the dies and a cover plate 20 supporting a spring 22. The member 16 and plate 20 are held together in any suitable manner. The holder may be mounted on a wheel (not shown) and the characters rolled into the workpiece.

While several embodiments of my invention have been shown and described, it will be apparent that other adaptations and modifications may be made without departing from the scope of the following claims.

I claim: 1. A stamping die for impressing a mark on a hot metal object comprising a body, a generally flat surface on said body, a

primary character of hard material extending outwardly fromsaid flat surface, and a secondary character of hard material closely surrounding said primary character and extending outwardly from said flat surface a distance less than said primary character, the surfaces of said secondary and primary characters being rounded.

2. A stamping die according to claim 1 in which said body and characters are made of hardened steel.

3. A stamping die according to claim 1 in which the primary character has a greater width than the secondary character.

4. A stamping die according to claim 3 in which said body and characters are made of hardened steel. 

